6.4 A special initiator tRNA starts the polypeptide chain [nitiation codon is a special codon (usually AUG)used to start synthesis of a protein. 清苇大兰
Initiation codon is a special codon (usually AUG) used to start synthesis of a protein. 6.4 A special initiator tRNA starts the polypeptide chain
6.4 A special initiator tRNA starts the polypeptide chain H % Blocked amino qroup Met-tRNAf N-formyl-met-tRNAf ■ 10-formyl tetrahydrofolate tetrahydrofolate Figure 6.11 The initiator N-formyl-methionyl-tRNA (fMet- tRNAf)is generated by formylation of methionyl-tRNA. using formyl-tetrahydrofolate as cofactor. 情華大当
Figure 6.11 The initiator N-formyl-methionyl-tRNA (fMettRNAf) is generated by formylation of methionyl-tRNA, using formyl-tetrahydrofolate as cofactor. 6.4 A special initiator tRNA starts the polypeptide chain
6.4 A special Only fMet-tRNA:enters partial P site on 305 initiator tRNA subunit bound to mRNA starts the [Me polypeptide chain Figure 6.12 Only fMet-tRNAf can be 50S subunit used for initiation by Only aa-tRNA enters 30S subunits;only A site on complete 70S ribosome other aminoacyl- tRNAs (aa-tRNA)can fMet be used for elongation by 70S ribosomes AUG NNN 清苇大兰
Figure 6.12 Only fMet-tRNAf can be used for initiation by 30S subunits; only other aminoacyltRNAs (aa-tRNA) can be used for elongation by 70S ribosomes. 6.4 A special initiator tRNA starts the polypeptide chain
6.4 A special initiator tRNA starts the polypeptide chain Fommylated amino acid 和g Met A A Figure 6.13 fMet- No base pairing Needed for fommylation Co tRNAf has unique features that GAC 6⊙ oc G C G distinguish it as the d initiator tRNA. GGDA GU G 3 G-C base pairs 8 Needed to enter P site 0 C 情莘大学 CA
Figure 6.13 fMettRNAf has unique features that distinguish it as the initiator tRNA. 6.4 A special initiator tRNA starts the polypeptide chain
F-3 305-mRNA com plex 6.4 A special initiator tRNA starts the polypeptide chain IF2-GTP joins com plex Figure 6.14 IF-2 is needed to bind fMet- fMet tRNAf to the 30S-mRNA Initiator tRNAjoins complex.After 50S binding,all IF factors are 50S subunitjoins and IF1-3 are release d小 released and GTP is M cleaved 清苇大当 IF-1 IF-2 IF-3 GDP P
Figure 6.14 IF-2 is needed to bind fMettRNAf to the 30S-mRNA complex. After 50S binding, all IF factors are released and GTP is cleaved. 6.4 A special initiator tRNA starts the polypeptide chain